Routing and topology management

ABSTRACT

A method for routing communications on a network node in a communications network includes: updating a central domain master regarding changes detected in topology, receiving a routing plan from the central domain master, where the routing plan is calculated at least in accordance with the changes, and transmitting data as necessary in accordance with the routing plan. A method implementable on a central domain master for routing communications between network nodes in a communications network includes receiving transmissions regarding changes detected in topology from the network nodes, calculating a routing plan based on at least the transmissions, and distributing the routing plan to the network nodes, where the central domain server is one of the network nodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit from U.S. Provisional Patent ApplicationNo. 61/290,228, filed Dec. 27, 2009, which is hereby incorporated in itsentirety by reference.

FIELD OF THE INVENTION

The present invention relates to network routing generally and torouting in a noisy environment in particular.

BACKGROUND OF THE INVENTION

A network's topology describes the layout of the network and determinesto a large extent how communications are routed from node to node on thenetwork. Common examples of topologies include: star topologies, wherecommunications are routed through a central or “master” node; bustopologies, where each node is connected to a common backbone or “bus”;and ring topologies, where each node is connected to two other nodes ina circular ring. A common feature of such topologies is that routingcommunications between participating nodes is relatively simple, theroute from one node to another is typically dictated unambiguously bythe topology itself.

Meshed topologies have layouts where at least some of the nodes havemultiple possible paths to other nodes. Accordingly, they requirerouting logic to determine a preferred route for communication betweentwo nodes. Such logic may include consideration for a number of factorsincluding, for example, bandwidth, line quality, and the number of“hops” between the participating nodes. Typically, a distributed methodmay be implemented wherein some or all of the participating nodesperiodically poll the “visible” network, i.e. the other nodes with whichthe polling node may effectively communicate. The polling results arethen analyzed in order to at least partially optimize routing betweenthe nodes.

G.hn data networks are designed to leverage previous investment in ahome by operating over existing wiring typically found in homes, suchas, for example, telephone wiring, coaxial cables and power lines. Thereis, however, a tradeoff for such leveraging. G.hn networks coexist withother technologies using the same wiring and the network's physicaltopology may typically be designed and implemented in accordance withthe requirements of those technologies. For example, telephone wiringtypically carries other analog and/or digital traffic and its coverageof the home may be limited—some rooms may not even have an outlet.Powerline implementations may be exposed to frequent power surges orspikes in accordance with the usage patterns of appliances sharing thesame medium. Under such circumstances there may be frequent interferenceon the G.hn network.

Reference is now made to FIG. 1A which illustrates an exemplary topology100 for a typical G.hn network. Areas A, B and C represent differentlogical areas within the network. Each such area represents a “fullymeshed” subset of the network; each node in a given area may generallybe capable of directly communicating with every other node in the samearea. For example, nodes 10, 11, 12 13, 14, and 15 may all be in area Aand capable of communicating with each other. Similarly, nodes 14-20 andnodes 19-23 may be in areas B and C respectively. The areas may overlapsuch that some nodes may be associated with more than one area. Forexample, nodes 14 and 15 may be in overlap area D, and may thereforedirectly communicate with each of the other nodes in both areas A and B.

There are instances of multiple possible routes between nodes intopology 100. For example, node 10 may use either node 14 or node 15 to“relay” a transmission to node 18. In fact, even if two nodes may be inthe same area and therefore capable of direct communications, there maybe other, possibly preferable, routing options. For example, the linebetween node 10 and node 13 may suffer from interference and/or haverelatively low bandwidth. Such interference may be intermittent suchthat the connection between the nodes is unreliable. If, for example,topology 100 describes a powerline network, there may be a refrigeratorlocated on the line between nodes 10 and 13. As the refrigerator'scompressor turns on and off, the power on the line may surge and theconnection between the nodes may temporarily break, or the effectiverate may be lowered. In such a case, it may be preferable to route theirmutual transmissions via node 11, even though a direct transmission pathmay at least nominally exist.

SUMMARY OF THE INVENTION

There is provided, in accordance with a preferred embodiment of thepresent invention, a method for routing communications on a network nodein a communications network, the method including: updating a centraldomain master regarding changes detected in topology, receiving arouting plan from the central domain master, where the routing plan iscalculated at least in accordance with the changes, and transmittingdata as necessary in accordance with the routing plan.

Further, in accordance with a preferred embodiment of the presentinvention, the updating includes transmitting the changes according to aroute included in the routing plan.

Still further, in accordance with a preferred embodiment of the presentinvention, the updating includes flooding the communications networkwith a transmission detailing the changes.

Additionally, in accordance with a preferred embodiment of the presentinvention, the flooding is performed only when the routing plan does notinclude a known usable route to the central domain master.

Moreover, in accordance with a preferred embodiment of the presentinvention, the flooding is performed whenever the changes are detected.

Further, in accordance with a preferred embodiment of the presentinvention, the flooding includes transmitting the changes to all othernetwork nodes in direct communication with the network node, andindicating to the other network nodes that they should retransmit thechanges to the central domain master, where the retransmitting is via atleast one of a route from the routing plan, and repeating the flooding.

Still further, in accordance with a preferred embodiment of the presentinvention, the method also includes repeating the flooding until anindication is received that the central domain master received thechanges.

Additionally, in accordance with a preferred embodiment of the presentinvention, the indication is an updated routing plan reflecting thechanges received from the central domain master.

Moreover, in accordance with a preferred embodiment of the presentinvention, the method also includes detecting the changes via at leastone of polling other network nodes, successfully communicating withother network nodes, experiencing a failed transmission with one othernetwork node, and monitoring communications between at least two othernetwork nodes.

Further, in accordance with a preferred embodiment of the presentinvention, the method also includes receiving at least one of a mediaaccess plan (MAP) and a repeated MAP (RMAP) generated by the centraldomain master, the MAP and RMAP including at least an indication of amost recent routing plan, and requesting an updated routing plan fromthe central domain master.

Still further, in accordance with a preferred embodiment of the presentinvention, the method also comprises initiating the updating when anindication does not indicate that the routing plan reflects at least thechanges, where the indication is included as part of the routing plan.

Additionally, in accordance with a preferred embodiment of the presentinvention, the method also comprises interpreting null entries in therouting plan as direct connections between two network nodes, where therouting plan includes at least a node to node routing table.

Moreover, in accordance with a preferred embodiment of the presentinvention, the method also includes detecting a broken link in therouting plan, using the routing plan to calculate an alternate routethat circumvents the broken link; and transmitting in accordance withthe alternate route.

Further, in accordance with a preferred embodiment of the presentinvention, the communications network is a G.hn network.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a method for routing communications between networknodes in a communications network, the method implementable on a centraldomain master, the method including receiving transmissions regardingchanges detected in topology from the network nodes, calculating arouting plan based on at least the transmissions, and distributing therouting plan to the network nodes, where the central domain server isone of the network nodes.

Further, in accordance with a preferred embodiment of the presentinvention, the calculating includes determining preferred routes betweeneach pair of the network nodes, and entering an indication of a firsthop for each preferred route in the routing plan, where if necessarysuccessive hops are determinable from other indications entered forother said pairs of network nodes along said preferred route.

Still further, in accordance with a preferred embodiment of the presentinvention, when the preferred route consists of only one hop, theindication is a null indication.

Additionally, in accordance with a preferred embodiment of the presentinvention, the communications network is a G.hn network.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1A is a schematic illustration of an exemplary network topology;

FIG. 1B is a schematic illustration of exemplary routing for updating anovel central domain master for the network of FIG. 1A;

FIG. 2 is a novel topology/routing manager to communicate with thecentral domain master of FIG. 1B, constructed and operative inaccordance with a preferred embodiment of the present invention;

FIGS. 3 and 4 are novel processes to be executed on the topology/routingmanager of FIG. 2;

FIG. 5 is a schematic illustration of routing for an exemplary networktopology; and

FIG. 6 is a novel routing table, constructed and operative in accordancewith a preferred embodiment of the present invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Some networks use domain masters (DMs) to provide centralizedfunctionality for the network. For example, a domain master node maydetermine and distribute media access plans (MAPs) to prevent collisionscaused by multiple nodes transmitting at the same time. Applicants haverealized that the routing used by the nodes may be improved bydesignating one of the nodes as a central domain master (DM) formonitoring changes in topology and using this information to determineoptimal routing plans. Topology information may be reported by each nodeto the domain master. In addition to the list of nodes that areaccessible to the reporting node, the topology information may alsoinclude details of quality level of the link.

Reference is now made to FIG. 1B which illustrates a preferred exemplaryembodiment of the present invention, constructed and operative inaccordance with a preferred embodiment of the present invention. Node 18in area B (FIG. 1A) may be assigned as central domain master 18′ fortopology/routing in the network of topology 100. Domain master 18′ mayreceive topology information directly from other nodes in area B. Nodesin areas A and C that may not have direct connections with DM 18′, suchas, for example, nodes 10-13 and nodes 21-23, may use the nodes in areasD and E to relay their topology information to DM 18′.

DM 18′ may use the cumulative information to monitor the network'stopology and to determine up-to-date optimal routing plans in accordancewith the topology's current state. DM 18′ may then distribute thecurrent topology and routing plans to the other nodes in area B. Nodesin areas D and E may relay this information to the nodes in areas A andC which may not be directly connected to DM 18′. It will be appreciatedthat the routing plans calculated and distributed by DM 18′ maythemselves indicate the routes by which they are distributed to nodesnot in direct contact with DM 18′.

In accordance with a preferred embodiment of the present invention, DM18′ may also determine and distribute MAPs for the network.

Reference is now made to FIG. 2 which illustrates a noveltopology/routing manager (TRM) 30, constructed and operative inaccordance with a preferred embodiment of the present invention. TRM 30may be implemented to provide node-level topology and routing managementon a node participating in a G.hn network, such as, for example, node 10in FIG. 1. TRM 30 may comprise a topology manager 40 and a routingmanager 60. Routing manager 60 may comprise routing interpreter 62 androuting calculator 64. TRM 30 may also comprise a transmitter/receiverinterface 50, which may enable TRM 30 to access built-in communicationsfunctionality as typically implemented on a network node.

Reference is now made to FIG. 3 which illustrates a novel centralizedrouting and topology management process 200, operative in accordancewith a preferred embodiment of the present invention. Process 200 may beexecuted by TRM 30 on a node participating in a G.hn network, such as,for example, node 10 in FIG. 1. TRM 30 may start (step 101) process 200as soon as node 10 registers to participate in the network, and maycontinue the process until the node resigns from participation.

Topology manager 40 may regularly use interface 50 to poll other networknodes to detect changes (step 110) in the node's topology. For example,in FIG. 1 node 10 may initially be in direct contact with nodes 11, 12,13, 14 and 15, all of which may be located in area A. However, overtime, the topology may change. For example, for whatever reason, node 10may no longer directly contact another node in area A, for example, node14. Similarly, circumstances may permit node 10 to eventually contact anode that may previously have been outside of area A, such as, forexample, node 16.

If a change may be detected, domain master 18′ may be contacted (step120) with information relevant to the change. For example, a message maybe sent to domain master 18′ indicating that the direct link with node11 may no longer be functioning. The details of how node 10 may contactDM 18′ are discussed in detail hereinbelow.

If no change was detected, processing may continue. Topology manager 40may periodically check (step 130) topology and routing information thatit may receive from DM 18′ via interface 50. Such information mayinclude updated details of topology 100 and instructions for preferredrouting of transmissions between participating nodes. It will beappreciated that the timing for the receipt of such information from theDM may be independent of the ongoing execution of process 200; topologymanager 40 may receive such information from time to time whenever itmay be sent by DM 18′.

It will be appreciated, that the polling required for step 110 may notnecessarily be explicit; manager 40 may use data from any of the ongoingcommunications to/from node 10. Manager 40 may also use data that it maydecode from the frame headers of transmissions that it may detectbetween other nodes.

Manager 40 may determine (step 135) whether the most recent topologyinformation received from the DM is current. Such determination may bebased on topology changes known to manager 40. For example, in step 110manager 40 may have identified that node 10 may no longer be incommunication with node 11. The most recently received topology/routinginformation may not be current if it does not reflect this change.

There may be other methods for determining that the topology/routinginformation may not be current. For example, in accordance with apreferred embodiment of the present invention, the DM may also calculateand distribute media access plans (MAPs). Each MAP may also include anindication, such as a serial number or the like, regarding the mostcurrent version of the topology/routing information. Accordingly,manager 40 may check that the topology information is current bycomparing its serial number to that included on the most recent MAPreceived from the DM.

If the topology/routing information may not be current, then TRM 30 maycontact DM 18′ via interface 50 with an update request in step 120,described in more detail hereinbelow. Once DM 18′ may be contacted withthe request, updated topology may eventually be received from the DM instep 130. It will be appreciated that step 120 may be performed in thebackground, or concurrently, with further processing. Accordingly, inaccordance with a preferred embodiment of the present invention,processing may continue to step 140 regardless of whether or not thetopology information is current. Alternatively, the processing ofprocess 200 may enter a brief wait state before executing step 130, thusproviding an opportunity for updated topology/routing information to bereceived from the DM.

TRM 30 may check interface 50 to determine whether or not there may bedata to transmit (step 140) to any other node on the network. If thereis no data to transmit, process 200 may loop back to step 110. If thereis data to transmit, TRM 30 may attempt to transmit (step 145) viainterface 50 as per the most recent topology information available. Asdiscussed in detail hereinbelow, routing interpreter 62 may providerouting instructions for the transmission. If the transmission issuccessful (step 150), i.e. there are no “broken links” with the targetnode, process 200 may loop back to step 110. It will be appreciated thatprocess 200 may pause for a pre-determined amount of time beforecontinuing with a next processing cycle.

However, if the transmission is not successful, step 120 may be invokedto update DM 18′ regarding the broken link with the target node. Inparallel, TRM 30 may attempt to retransmit (step 145) the data to thetarget node. After several failed retries, routing manager 60 may invokerouting calculator 64 to calculate (step 155) an alternate route basedon the current topology/routing information as known to TRM 30. Ifcalculator 64 successfully resolves (step 160) a new route, processingmay return to step 145 for transmission as per the calculated routing.If step 160 is unsuccessful, then step 120 may be invoked to requestupdated topology information from DM 18′ and the process may loop backto step 130 to await the requested update.

Reference is now made to FIG. 4 which details process 120, operative inaccordance with a preferred embodiment of the present invention. Asindicated in FIG. 3, process 120 may be invoked in response to amultiplicity of conditions that may occur during process 200. Forexample, process 120 may be invoked from step 110 if topology manager 40detects a change in topology. Similarly, process 120 may be invoked fromstep 135 if topology manager detects that the current topologyinformation does not match the current version indicated on the mostrecently received MAP. Process 120 may also be invoked from step 160 ifrouting calculator 64 is unable to successfully calculate a route to theDM, i.e. if the link to DM 18′ is broken. Process 120 may also beinvoked on startup, i.e. the first time topology manager 40 performsstep 110. A topology change may always be detected upon startup; a nodemay not “remember” topologies from previous registrations.

It will be appreciated that whenever process 120 may be invoked, one ormore parameters may be input to it to indicate the nature of theprocessing involved. For example, when invoked from step 110, theparameters may include a “New topology information” request as well asthe information itself. Such information may include, for example, thedetails of a broken link recently identified by the node. When invokedfrom steps 135 or 160, the parameters may include a “topology update”request, an indication of the step from which it was invoked, and anidentifier for the requesting node.

In process 120, TRM 30 may initially access routing manager 60 todetermine (step 121) whether or not a valid link or route exists to DM18′ and if so, it may use interface 50 to transmit (step 122) therelevant request via the identified link/route. In accordance with apreferred embodiment of the present invention, a valid link to thedomain master may be assumed to exist if the node either directlyreceives MAPs from the DM or if it indirectly receives repeated MAPs(RMAPs) that may have been relayed by other nodes.

It will be appreciated that, in some cases, routing manager 60 may beunable to provide a valid link/route. For example, at the very beginningof process 200 there may not yet be an identified link/route to DM 18′.The topology change identified in step 110 may have involved aninability to contact DM 18′. Furthermore, invoking process 120 from step160 may indicate that routing manager 60 may have already unsuccessfullytried to resolve a route to the DM. In such cases, processing maycontinue directly from step 121 to step 124 (flooding) as discussed indetail hereinbelow.

Interface 50 may indicate (step 123) whether or not the transmission wassuccessful. If successful, process 120 may exit to step 130 (FIG. 3) toawait updated topology/routing information to be received from DM 18′.It will be appreciated that transmitting to the DM may require more thanone “hop”. For example, in FIG. 1, a transmission from node 10 to node18 may be relayed via nodes 14 or 15. It is therefore possible that,even though the transmission to the relay node (i.e. node 14 or 15) maybe successful, the next hop may fail. In such a case, TRM 30 may detectin steps 130 and 135 (FIG. 3) that DM 18′ may not have been updated withthe current topology and process 120 may be invoked again. In accordancewith a preferred embodiment of the present invention, if process 120 isrepeatedly invoked in such manner more than a predefined limit it may bedetermined that the transmission of step 122 was unsuccessful.

If step 122 is unsuccessful, TRM 30 may use interface 50 to flood (step124) the network with the relevant request to update the domain masterabout the broken link. The node may attempt to transmit the request andits relevant parameters (for example a “new topology request”, anidentifier for the node and its current topology information) to everyother node with which it is in contact. For example, using theembodiment of FIG. 1, node 10 may “flood” area A by sending such atransmission to each of the nodes with which it is in communication,i.e. each node in area A.

Each of the nodes in area A may continue the “flooding” by similarlyretransmitting the transmission to each of the nodes with which they arein communication, except for the node(s) from which it received theflooded message. For example, in FIG. 1 nodes 14 and 15 may be locatedin both areas A and B. Accordingly, in such manner, either or both ofthese nodes may succeed in forwarding the transmission to DM 18′ in areaB.

After flooding may be initiated in step 124, processing may continueafter a pre-defined pause in step 130 of process 200. If revisedtopology/routing information including the requested update has beenreceived from the DM, process 200 may continue as disclosed hereinabove.If the topology/routing information is not current (step 135), i.e. notupdated with the expected information, process 120 may be invoked againto continue the flooding process. During “flooding” it may be assumedthat a valid link may not exist with DM 18′. Accordingly, processing mayflow directly to step 124 and the network may be flooded (step 124)again. This processing may continue repeatedly until updatedtopology/routing information may be received from DM 18′. Accordingly,once a “flooding” node receives routing information from the DM thatcontains the identified topology message it will discontinue floodingthe identified topology message.

It will be appreciated that the timing between flooding cycles may beregulated by adding pauses before at least one of the steps. Forexample, processing may pause for 250-500 milliseconds before step 130to provide a window of time for DM 18′ to receive the update request,calculate new optimal routes and transmit to the node.

It will be appreciated that the processing capabilities of the differentnodes participating in the network may vary. Some nodes may be capableof calculating generally optimal routing plans without having to rely onplans distributed by DM 18′. It will also be appreciated, that in somenetwork environments there may be a high level of relatively frequentinterference that may render dependence on a central DM unreliable.Applicant has realized that in such situations a “hybrid” approach,incorporating a central DM with distributed routing may be advantageous.Therefore, in accordance with a preferred alternate embodiment of thepresent invention, every node that may experience a change in itstopology information may send topology updates to all of the other nodesby a flooding method, regardless of whether or not it may capable ofsending the updates to Domain Master 18′, either directly or indirectlyvia relay nodes.

The ongoing processing for the hybrid approach may be generally similarto that of process 200. However, instead of using process 120 whennecessary to contact the DM, step 124 may be invoked directly to floodthe network regardless of the status of connection with the DM.Processing may then continue to step 130 as in process 120 followingflooding.

In such an embodiment DM 18′ may continue to calculate and distributeoptimal routing plans based on the received topology. However, since theentire network may be flooded with updates on a regular basis, a typicalnode may have generally up-to-date information even if it may not have areliable route to/from DM 18′. Each node shall use routing plansdistributed by DM 18′. However, where a node may determine that the lastdistributed routing plans are not valid, then the node may replace thedistributed routing plans with recalculated routes based on ongoingtopology updates. Such “locally” calculated routes may then be replacedthe next time an update may be received from DM 18′.

In accordance with a preferred embodiment of the present invention, therouting plans distributed by DM 18′ may be compressed to reduce thebandwidth requirements for repeated distribution. It will be appreciatedthat such compression may significantly reduce the overhead for routingupdates in an environment that may suffer from frequent interference.

The routing plans may be compressed using the following method: Therouting plans that may be distributed by the DM may not specify everysingle possible route between two given nodes in the domain. Instead,the routing plans may indicate how every given node may reach any othergiven node in the domain by specifying only the next relay node along anoptimal path towards the final destination node. Although the routingplans may therefore include only the next hop in the optimal pathtowards each node, it will be appreciated that the information may alsoprovide indications of alternative non-optimal routes due to propagationof the information.

Reference is now made to FIG. 5 which illustrates an exemplary networktopology 300. Each node in areas A, B and C may communicate with anyother node in the same area. Some nodes, such as nodes 5, 6, and 7, maybe in the intersection between two areas; such nodes may be used torelay transmissions between other nodes located in just one of the sametwo areas. For example, node 5 may relay transmissions between nodes 1and 8. The arrows may indicate optimal routing as determined by the DMfor the depicted domain.

As discussed hereinabove, there may be many factors affecting optimalrouting in a network, including, for example, physical (PHY) metrics(such as signal to noise ratio, actual rate, etc.), available bandwidth,quality of service constraints, local PHY conditions, and the need tobalance the requirements for each of the participating nodes. Thepresent invention may employ any appropriate algorithm for determiningrouting between nodes. It will be appreciated that since the primaryrouting function may be performed by the DM on behalf of all the nodesin the domain, the required application may be implemented in just thedomain master. Accordingly, only one node (the domain master) may beaffected when the application may be updated or replaced.

Reference is now made to FIG. 6 which illustrates an exemplary optimalrouting table 400 for the domain of FIG. 6 as determined by a routingalgorithm on the DM. The rows of table 400 may represent transmittingnodes; the columns may represent a target node to receive atransmission. Each entry in the table may specify the relay node thatmay relay the transmission from the transmitter (line index) to thedestination node (column index). Table 400 may be distributed by the DMand may be interpreted by routing interpreter 62 (FIG. 2) as necessaryto determine the route by which a transmission may be sent to any othernode in the domain.

It will be appreciated that most of the entries in table 400 may beempty. A null, or empty, entry may indicate a direct connection betweenthe transmitting and receiving node. For example, the entry for row 2,column 5 may be empty, thus indicating that nodes 2 and 5 may be in thesame area (for example, area A in FIG. 5) and may communicate directlywithout intermediate relay nodes. The entry for row 2, column 8 may be“5”, thus representing an optimal route for transmitting from node 2 tonode 8 via node 5.

In some cases, multiple hops may be required for the transmission. Forexample, the transmitting from node 2 to node 11 may require twointermediate relay nodes. In such a case, only the first intermediaterelay node may be indicated in table 400, i.e. “6” as shown in row 2,column 11. It may not be necessary to add an explicit entry for thesecond hop (i.e. “9”) because table 400 may already comprise theinformation required to determine the full route. In order to transmitfrom node 2 to node 11, node 2 may transmit to node 6. Upon receipt ofthe transmission, routing interpreter 62 on node 6 may use its copy oftable 400 to determine that the optimal route from node 6 to node 11 maybe via node 9 and transmit accordingly. When node 9 may receive thetransmission, it may use its copy of table 400 to determine that node 11may be in the same area (i.e. area C as per FIG. 5) and relay thetransmission directly to node 11.

It will be appreciated that the exemplary labeling of the nodes in thedomain of FIG. 5 may be generally simplistic for illustration purposes.Nodes may typically be identified by character strings longer than justone or two digits. Accordingly, it will be appreciated that using nullentries instead of explicit entries to indicate nodes in the same areaof the domain may significantly reduce the size of table 400.Furthermore, the implicit provision of additional hop routing maysignificantly simplify the data structure required for table 400,further serving to reduce its size. Accordingly, the distribution ofoptimal routing logic via table 400 may significantly reduce theduration of such transmissions, thus reducing overhead in terms ofexposure to network congestion.

Unless specifically stated otherwise, as apparent from the abovediscussions, it is appreciated that, throughout the specification,discussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer, computing system, or similar electroniccomputing device that manipulates and/or transforms data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices.

Embodiments of the present invention may include apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the desired purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a computer readable storage medium, such as, but not limitedto, any type of disk, including floppy disks, optical disks,magnetic-optical disks, read-only memories (ROMs), compact discread-only memories (CD-ROMs), random access memories (RAMs),electrically programmable read-only memories (EPROMs), electricallyerasable and programmable read only memories (EEPROMs), magnetic oroptical cards, Flash memory, or any other type of media suitable forstoring electronic instructions and capable of being coupled to acomputer system bus.

The processes and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the desired method. The desired structure for avariety of these systems will appear from the description below. Inaddition, embodiments of the present invention are not described withreference to any particular programming language. It will be appreciatedthat a variety of programming languages may be used to implement theteachings of the invention as described herein.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

What is claimed is:
 1. A method for routing communications on a networknode in a communications network, said method comprising: updating acentral domain master regarding changes detected in topology; attemptingto receive at all network nodes in the communications network a samerouting plan from said central domain master, wherein said same routingplan includes data describing a route between each of said network nodesand all other nodes in said communication network, and wherein saidrouting plan is calculated at least in accordance with said changes;receiving at least one of a media access plan (MAP) and a repeated MAP(RMAP) generated by said central domain master, said MAP and RMAPincluding at least an indication of a most recent routing plan;comparing said indication of a most recent routing plan with informationassociated with a version of said received same routing plan; andrequesting an updated routing plan from said central domain masterresponsive to said comparison.
 2. The method according to claim 1 andwherein said updating comprises transmitting said changes according to aroute included in said routing plan.
 3. The method according to claim 1and wherein said updating comprises: flooding said communicationsnetwork with a transmission detailing said changes.
 4. The methodaccording to claim 3 and wherein said flooding is performed only whensaid routing plan does not include a known usable route to said centraldomain master.
 5. The method according to claim 3 and wherein saidflooding is performed whenever said changes are detected.
 6. The methodaccording to claim 3 and wherein said flooding comprises: transmittingsaid changes to all other said network nodes in direct communicationwith said network node; and indicating to said other network nodes thatthey should retransmit said changes to said central domain master;wherein said retransmitting is via at least one of: a route from saidrouting plan, and repeating said flooding.
 7. The method according toclaim 3 and also comprising repeating said flooding until an indicationis received that said central domain master received said changes. 8.The method according to claim 7 and wherein said indication is anupdated said routing plan reflecting said changes received from saidcentral domain master.
 9. The method according to claim 1 and alsocomprising detecting said changes via at least one of: successfullycommunicating with other said network nodes; experiencing a failedtransmission with one said other network node; and monitoringcommunications between at least two said other network nodes.
 10. Themethod according to claim 1 and also comprising: initiating saidupdating when an indication does not indicate that said routing planreflects at least said changes, wherein said indication is included aspart of said routing plan.
 11. The method according to claim 1 and alsocomprising interpreting null entries in said routing plan as directconnections between two said network node, wherein said routing planincludes at least a node to node routing table.
 12. The method accordingto claim 1 and also comprising: detecting a broken link in said routingplan; using said routing plan to calculate an alternate route thatcircumvents said broken link; and transmitting in accordance with saidalternate route.
 13. The method according to claim 1 and wherein saidcommunications network is a G.hn network.
 14. The method according toclaim 1 wherein said routing plan comprises an indication of a first hopfor each said route between each two said network nodes.
 15. The methodaccording to claim 1 wherein said indication comprises a serial numberof said most recent routing plan.
 16. A method for routingcommunications between network nodes in a communications network, saidmethod implementable on a central domain master, the method comprising:calculating a routing plan based on at least transmissions receivedregarding changes detected in topology from said network nodes;distributing a same routing plan to all network nodes in thecommunications network, wherein the central domain master is one of saidnetwork nodes-and wherein said same routing plan includes datadescribing a route between each of said network nodes and all othernodes in said communication network; transmitting at least one of amedia access plan (MAP) and a repeated MAP (RMAP) by said central domainmaster, said MAP and RMAP including at least an indication of a mostrecent routing plan; and transmitting an updated routing plan uponreceiving a request responsive to a comparison of said indication of amost recent routing plan with information associated with a version ofsaid distributed same routing plan.
 17. The method according to claim 14and wherein said calculating comprises; determining preferred routesbetween each pair of said network nodes; and entering an indication of afirst hop for each said preferred route in said routing plan, wherein ifnecessary successive hops are determinable from other said indicationsentered for other said pairs of network nodes along said preferredroute.
 18. The method according to claim 17 and wherein when saidpreferred route consists of only one hop, said indication is a nullindication.
 19. The method according to claim 16 and wherein saidcommunications network is a G.hn network.
 20. The method according toclaim 16 wherein said version information comprises a serial number ofsaid most recent routing plan.